I feel like you're ignoring a whole host of variables with a reductionist statement like "they commit more crimes proportionally". First of all, how do you compare what "more crimes" is proportionally? Different countries have vastly different definitions of what constitutes a crime, and further, different penalties for those crimes.
Even if you did isolate those factors, it's still not really an answer to "why does this happen more here than there?" You're answer is, essentially, "because it happens more often there."
Edit: After rereading the second paragraph I realize that you do seem to be pointing towards solutions to the root cause of crime rates, but I find the first statement confusing in light of that.
Even if you did isolate those factors, it's still not really an answer to "why does this happen more here than there?" You're answer is, essentially, "because it happens more often there."
Edit: After rereading the second paragraph I realize that you do seem to be pointing towards solutions to the root cause of crime rates, but I find the first statement confusing in light of that.